Re: Inclusion of x86_64 memorize ioapic at bootup patch

[Yinghai Lu <yinghai.lu@amd.com>]

the patch is good.

I tried LinuxBIOS with kexec.

without this patch: I need to disable acpi in kernel. otherwise the
kernel with acpi support can boot the second kernel, but the second
kernel will hang after

time.c: Using 14.318180 MHz HPET timer.
time.c: Detected 2197.663 MHz processor.
Console: colour VGA+ 80x25
Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes)
Inode-cache hash table entries: 65536 (order: 7, 524288 bytes)
Memory: 1009152k/1048576k available (2967k kernel code, 39036k reserved, 1186k )


YH

On 1/2/06, Vivek Goyal <vgoyal@in.ibm.com> wrote:
> Hi Andi,
>
> Can you please include the following patch. This patch has already been pushed
> by Andrew.
>
> http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.15-rc5/2.6.15-rc5-mm3/broken-out/x86_64-io_apicc-memorize-at-bootup-where-the-i8259-is.patch
>
> This patch is regarding remembering at boot up time where i8259 is connected
> and restore the APIC settings back during kexec boot or kdump boot. This
> enables getting timer interrupts in new kernel in legacy mode.
>
> This patch is needed to make kexec and kdump work on some systems,
> especially opteron boxes. Otherwise the second kernel does not receive
> timer interrupts during early boot hence hangs.
>
> I understand, that you are inclined towards remembering all the APIC states
> and simply restore it back instead of putting hooks. This will work
> well for kexec but not for kdump because in kdump system can crash on
> non-boot cpu.
>
> Restoring BIOS APIC state can make sure that BIOS designated boot cpu will
> always be able to see timer interrupts in legacy mode but same does not
> hold good if new kernel boots on some other cpu as is the case with kdump.
>
> In case of kexec boot, we relocate to boot cpu but in case of kdump we
> don't because it was suggested that in some extreme cases of crash, boot cpu
> might not respond even to NMI and relocation to boot cpu will not be
> possible.
>
> Can you please re-consider this patch for inclusion.
>
> Thanks
> Vivek
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